LEVEES. 79 



In regard to the slopes given to levees in America, another author* states that 

 "the slopes of 3 to i now generally adopted are the outcome of a long experience. In 

 the early stages of levee building, much smaller dimensions were often used, but disaster 

 was frequently the result. A steep back slope very often leads to extensive sloughing 

 or slipping, especially if the material be at all weak. A steep front slope exposes the 

 embankment to serious abrasion by waves. A slope of 2 to i is less than the angle of 

 repose of wet earth of almost any kind. In very small levees, where the width of the 

 crown cuts an important figure, slopes may often be reduced. Thus a levee 3 feet 

 high, with a crown of 8 feet and slopes of 2 to i, has a stronger section than a levee 12 

 feet high with slopes of 3 to i. 



" Where the exposure to winds is very great the front slope is often made as flat 

 as 5 to i, the back slope being then reduced to 2 or 2.5 to i. It is found that a flat 

 slope is a great protection against the wash of waves, and that a well-sodded 'buck- 

 shot' levee, with a slope of 5 to i, will stand a pretty stiff wind. If the sod be once 

 cut through, however, and a hole made in the clay, the latter is liable to be undermined, 

 and the superincumbent masses of earth fall in huge blocks." 



The following gives information as to the sections generally used:f 



"A few years ago the Government adopted standard sections which have since 

 been adhered to, except in cases where the conditions demanded more specific treat- 

 ment. The first, second, and third districts of the Mississippi River have practically 

 the same standard for all levees on ordinarily good foundations, and when constructed 

 of material not below the average in strength. 



"The standard dimensions are: Crown, 8 feet; front or river slope, 3 to i ; back 

 slope, 3 to i. Where the levee is over n feet in height, a banquette, at an elevation 

 of 8 feet below the top of the main levee, is added. The slope of the crown of this 

 banquette is 10 to i, width of crown 20 feet, and back slope 4 to i. Where the foun- 

 dation is bad, or the material weak, the banquette section, and perhaps the front slope 

 of the main levee, is increased. 



"The specifications require the levee to be constructed in 2 -foot layers, with scrapers, 

 on a well-grubbed and thoroughly plowed foundation containing a small exploration 

 muck-ditch filled back with strong material, the best to be found in the vicinity, and 

 sodded at 2 -foot intervals with Bermuda grass. 



" In the fourth district the dimensions of the standard adopted vary with the height, 

 and are intended to conform more nearly to the supposed theoretically perfect section. 

 These variations may be further modified, as in the other districts, when required by 

 abnormal condition of foundation, material of construction, wave wash, etc. 



" For levees from 5 to 10 feet in height, the crown is 8 feet, the river slope is 3 to i, 

 and the land slope 2^ to i. 



"For levees from 10 to 15 feet in height the crown is 8 feet, the river slope is 3 to 



* Levees of the Mississippi, Wm. Starling. f Standard Levee Sections, H. Coppee. 



